The present patent application claims priority from Japanese patent applications Nos. H. 11-139683 filed on May 20, 1999, H. 11-147538 filed on May 27, 1999 and H. 11-256522 filed on Sep. 10, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid container equipped with a piezoelectric apparatus therein which detects the consumption state of liquid inside a liquid container which houses the liquid, by means of detecting change of the level of the acoustic impedance, especially detecting the change of the resonant frequency. More particularly, the present invention relates to the piezoelectric apparatus detecting ink consumption in an ink cartridge and a mounting module member thereof, which are provided in the ink cartridge for use with an ink-jet recording apparatus. The ink-jet recording apparatus performs the printing operation by discharging ink droplets from a nozzle opening, in a manner such that ink in a pressure generating chamber is compressed by a pressure generating means corresponding to printing data.
2. Description of the Related Art
An ink cartridge mounted on an ink-jet type recording apparatus is taken as an example of a liquid container and is described below. In general, an ink-jet recording apparatus comprises: a carriage equipped with an ink-jet type recording head comprised of a pressure generating means which compresses a pressure generating chamber and a nozzle opening which discharges the compressed ink from a nozzle opening in the form of ink droplets; and an ink tank which houses ink supplied to the recording head through a passage, and is structured such that the printing operation can be performed continuously. In general, the ink tank is structured as a cartridge that can be detached from the recording apparatus, so that a user can easily replace it at the time when the ink is used up.
Conventionally, as a method of controlling the ink consumption of the ink cartridge, a method is known of controlling the ink consumption by means of a calculation in which the counted number of ink droplets discharged by the recording head and the amount of ink sucked in a maintenance process of the printing head are integrated by software, and another method of controlling the ink consumption in which the time at which the ink is actually consumed is detected by directly mounting to the ink cartridge two electrodes for use in detecting the liquid surface, and so forth.
However, in the calculation-based method of controlling the ink consumption by integrating the discharged number of ink droplets and the amount of ink or the like by the software, the pressure inside the ink cartridge and the viscosity of the ink change depending on usage environment such as ambient temperature and humidity, elapsed time after an ink cartridge has been opened for use, and usage frequency at a user side. Thus, a problem is caused where a considerable error occurs between the calculated ink consumption and the actual ink consumption. Moreover, another problem is caused in which the actual amount of ink remaining is not known because once the same cartridge is removed and then mounted again, the integrated counted value is reset.
On the other hand, in the method of controlling by electrodes the time at which the ink is consumed, the remaining amount of ink can be controlled with high reliability since the actual ink consumption can be detected at one point. However, in order that the liquid surface of the ink can be detected, the ink need be conductive, so suitable types of ink for use are very limited. Moreover, a problem is caused in that a fluid-tight structure between the electrodes and the cartridge might be complicated. Moreover, since precious metal is usually used as the electrode material, which is highly conductive and erosive, manufacturing costs of the ink cartridge increases thereby. Moreover, since it is necessary to attach the two electrodes to two separate positions of the ink cartridge, the manufacturing process increases, thus causing a problem which increases the manufacturing costs.
Therefore, it is an object of the present invention to provide a liquid detecting piezoelectric device capable of reliably detecting a liquid consumption status and dispensing with a complicated sealing structure. It is another object of the present invention to provide an ink cartridge capable of reliably detecting a liquid consumption status by use of a liquid detecting piezoelectric device and capable of dispensing with a complicated sealing structure. It is still another object of the present invention to provide a detection device capable of reliably detecting a liquid consumption status. It is still another object of the present invention to provide a mounting module for use in detecting liquid, capable of reliably detecting a liquid consumption status and capable of dispensing with a complicated sealing structure. It is still another object of the present invention to provide a liquid container capable of reliably detecting a liquid consumption status and capable of dispensing with a complicated sealing structure. These objects are achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to an aspect of the present invention, there is provided a piezoelectric device, mounted on a liquid container, for detecting a liquid consumption status of the liquid contained in the liquid container, comprising: a vibrating section which generates vibration by deforming a piezoelectric element, wherein the vibrating section is preferably symmetrical about a center thereof.
Moreover, it is preferable that the vibrating section of the piezoelectric device is of a substantially circular shape. Moreover, the piezoelectric device comprises: a piezoelectric layer; an upper electrode provided on an upper surface of the piezoelectric layer; a lower electrode provided on a lower surface of the piezoelectric layer; and a vibrating plate having a first surface contacting the lower electrode and a second surface a part of which contacting the liquid contained in the liquid container, wherein at least part of the piezoelectric layer, the lower electrode and the vibrating plate constitute the vibrating section. Moreover, it is preferable that respective main portions of the piezoelectric layer are approximately concentrically circular with the vibrating section.
Moreover, it is preferable that the piezoelectric device further comprises a base plate having an upper surface contacting the lower surface of the vibrating plate and a lower surface contacting the liquid contained in the liquid container. It is preferable that the base plate includes a cavity which contacts and holds the liquid contained in the liquid container. It is preferable that the cavity is approximately concentrically circular with the vibrating section. Moreover, it is preferable that the deformation of the vibrating plate due to a residual vibration is greater than that of the base plate. An edge of vibration of the vibrating section locates in the vicinity of an outer periphery of the cavity. It is preferable that the piezoelectric device further comprises a mounting member having an upper surface contacting the lower surface of the vibrating plate and a lower surface facing inside the liquid container, and the mounting member has an opening corresponding to a center of the vibrating section. Moreover, preferable is the liquid container mounting the above the piezoelectric device
According to another aspect of the present invention, it is preferable that a module comprises: the piezoelectric device; and a mounting structure formed integrally with the piezoelectric device for mounting the liquid detection device onto the liquid container.
The mounting structure may include a projected portion which is projected inward the liquid container, and a center of the vibrating section maybe arranged on a center line of the projected portion. Moreover, the projected portion may be of a circular shape. It may further comprise a terminal which provides a drive signal to the upper electrode and lower electrode of the piezoelectric device. Moreover, preferable is the liquid container mounting the above module. Moreover, the liquid container may be an ink cartridge which houses ink supplied to an ink-jet recording apparatus.
According to another aspect of the present invention, there is provided a piezoelectric device, mounted on a liquid container, for detecting a liquid consumption status of the liquid contained in the liquid container, comprising: a vibrating section which generates vibration including: a vibrating plate whose one surface contacts the liquid in the liquid container; a lower electrode formed in other surface of the vibrating plate; a piezoelectric layer, formed on the lower electrode, which vibrates the vibrating plate by oscillation caused by piezoelectric phenomenon; an upper electrode formed on the piezoelectric layer, wherein it is preferable that the vibrating section is formed so that the piezoelectric layer covers the lower electrode and that the upper electrode covers the lower electrode and that the piezoelectric layer is protruded from the upper electrode.
Moreover, it is preferable that the piezoelectric device further comprises a base plate having an upper surface contacting the lower surface of the vibrating plate and a lower surface contacting the liquid contained in the liquid container, and that the base plate includes a cavity which contacts the liquid at a position of a vibrating portion of the vibrating plate. Moreover, it is preferable that the area of the cavity is greater than that of the lower electrode. It is preferable that the compliance of the vibrating plate due to residual vibration is greater than that of the base plate. The area of a piezoelectric layer portion generating the piezoelectric effect may be approximately same as that of the lower electrode. The respective main portions of the upper electrode, piezoelectric layer and lower electrode are preferably rectangular. The respective main portions of the upper electrode, piezo electric layer and lower electrode maybe circular. It is preferable that the cavity is substantially circular and that a ratio of a radius of the cavity to a depth thereof is greater than 3xcfx80/8. It is preferable that the piezoelectric device detects the consumption status of the liquid inside the liquid container by detecting change in the acoustic impedance in the vicinity of the vibrating section. In the piezoelectric device, it is preferable that a counter electromotive force is generated by the residual vibration caused by the vibration of the piezoelectric layer and that the liquid consumption status in the liquid container is detected by detecting a change in the acoustic impedance. Moreover, preferable is the liquid container mounting the above piezoelectric device.
According to still another aspect of the present invention, there is provided a module, mounted on a liquid container, for detecting a liquid consumption status of the liquid contained in the liquid container, comprising: a piezoelectric device which detects the liquid consumption status by generating the counter electromotive force by the residual vibration which remains after vibration; a mounting structure formed integrally with the piezoelectric device, wherein the piezoelectric device comprises: :a vibrating plate whose one surface contacts the liquid in the liquid container; a lower electrode formed in other surface of the vibrating plate; a piezoelectric layer formed on the lower electrode; an upper electrode formed on the piezoelectric layer, wherein it is preferable that the piezoelectric layer is formed so as to cover the lower electrode, the upper electrode covers the lower electrode and the piezoelectric layer is protruded from the upper electrode.
Moreover, the mounting structure is preferably such that the upper surface contacts the lower surface side of the vibrating, which is in contact with the liquid, the lower surface has amounting member which is in contact with the liquid in the liquid container, and the mounting member has a cavity which is in contact with the liquid at a position of a vibrating portion of the vibrating plate. Moreover, the area of the cavity is preferably larger than that of the lower electrode. It is preferable that the cavity is substantially circular and that a ratio of a radius of the cavity to a depth thereof is greater than 3xcfx80/8. The mounting structure of the module may have an opening in its center and that the piezoelectric device may be arranged in the opening. Moreover, the area of the opening is preferably larger than that of a piezoelectric effect generating portion of the piezoelectric layer. Moreover, the piezoelectric device may be provided in a detachable manner. Moreover, preferable is a liquid container in which the above module is arranged.
In a preferred embodiment, there are provided a liquid container housing the liquid, a liquid detecting device mounted to the liquid container and a mounting module therefor which are used for detecting the liquid consumption status in the liquid container. The liquid detecting device includes a piezoelectric element, and the piezoelectric element outputs a signal corresponding to the liquid consumption status by conversion between electric energy and vibration energy. The piezoelectric element is formed on a base member. In particular, an opening cavity is provided in the base member. The opening cavity is provided in a position counter to the piezoelectric element so as to communicate with an interior portion of the liquid container. It is preferable that the opening cavity be provided in a position directed toward the interior portion of the ink container so as to communicate with the interior portion of the ink container.
In the state where the liquid consumption has not yet progressed, the inside and outside of the opening cavity are filled with the liquid. On the other hand, when the liquid consumption progresses, the liquid surface is lowered and then the opening cavity is exposed. Then, an approximately fixed amount of the liquid remains in the opening cavity. Utilizing the fact that the output signals of the piezoelectric element differ in these two states, the liquid consumption state can be suitably detected.
According to the present invention, an embodiment thereof can be designed so that erroneous detection due to undulated liquid wave caused by provision of the cavity can be avoided.
Moreover, according to the present invention, by providing the cavity the number of members to be placed between the piezoelectric element and the liquid can be reduced, or the thickness of such members can be reduced, so that the liquid consumption state can be further reliably detected.
Moreover, according to the present invention, by providing the opening cavity locally, an appropriate liquid sealing state can be realized by utilizing a surrounding base member thereof. Thereby, exposure of the piezoelectric element to the liquid can be avoided. This is particularly effective for the conductive-like liquid such as ink.
Preferably, utilizing the piezoelectric element, the liquid consumption state is detected based on the change in the acoustic impedance corresponding to the liquid consumption status. Preferably, the piezoelectric element outputs a signal indicating the residual vibration state after vibration has been applied. The residual vibration of the piezoelectric element changes depending on the surrounding liquid. For example, the residual vibration states differ between when the large amount of liquid is present and when the small amount of liquid is present. This is based on the change in the acoustic impedance according to the liquid consumption state. Thus, the liquid consumption state is detected utilizing the fact that the residual vibration state changes according to the liquid consumption state.
Here, it is to be noted that a limited amount of liquid in the close vicinity of the piezoelectric element is one that substantially affects the residual vibration. According to the present invention, by provision of the opening cavity the number of intermediate members to be placed between the piezoelectric element and the liquid can be reduced, or the thickness of such members can be reduced. Thus, the limited amount of liquid affecting the residual vibration approaches or comes in contact with the piezoelectric element. Thereby, the change of the residual vibration corresponding to the liquid consumption state becomes clearer, so that the liquid consumption state can be further reliably detected.
Moreover, the piezoelectric element may not only generate the elastic wave through the opening cavity, but also output a signal corresponding to the reflected wave which is reflected back through the opening cavity. In this case too, since the vibration is satisfactorily transferred in between the piezoelectric element and the liquid by providing the opening cavity, detection capacity-can be improved. How the piezoelectric element plays a role in the course of detecting the liquid consumption state may be determined according to the specifications of the liquid container and a required measurement accuracy.
The liquid detecting device according to the present invention, may generate a detection signal indicating the residual vibration state corresponding to the liquid inside the opening cavity when the liquid comes to a state of being held inside the opening cavity in a detection-targeted predetermined liquid consumption state.
The opening cavity is preferably of a shape which holds the liquid in a predetermined liquid state. The opening cavity is preferably of a shape which still holds the liquid in the detection-targeted predetermined liquid consumption state.
The opening cavity may penetrate the base member. An intermediate member may be provided between the piezoelectric element and the base member. The intermediate member seals off the opening cavity and vibrates together with the piezoelectric element.
Preferably, the piezoelectric element includes a lower electrode formed on the base member, a piezoelectric layer formed on the lower electrode, and an upper electrode formed on the piezoelectric layer. An opening area of the opening cavity in the piezoelectric element side is set to be greater than that of the overlapped portion of the piezoelectric layer and the lower electrode.
Preferably, the depth of the cavity is set to be less than the narrowest width of a cavity opening. Preferably, the depth of the cavity is less than one third of the narrowest width of the cavity. If the cavity is of a circular shape, the opening narrowest-width will be an opening dimension (opening diameter).
Preferably, the opening cavity has a shape substantially symmetrical about the center of the piezoelectric element. Preferably, the opening cavity is of a substantially circular shape.
Preferably, an opening area of the opening cavity inside the container is set to be greater than that in the piezoelectric element side. The opening dimension in the piezoelectric element side is preferably greater than that inside the container. Configured in this manner, the opening cavity is of a shape that radiates inwardly toward the inside of the container. The peripheral surface of the opening cavity may be of a tapered shape. The peripheral surface of the opening cavity may be of a stepped shape.
A communicating groove which communicates with the opening cavity may be provided in the base member. The communicating groove being provided on the base member is provided in a portion facing the inside of the container. The communicating groove may be provided along a direction toward a supply port by which the liquid container supplies the liquid to the outside thereof.
The liquid detecting device may be formed integrally with the mounting structure for mounting to the liquid container. A module is constructed by integrating the liquid detecting device with the mounting structure.
Still another embodiment of the present invention is a liquid container equipped with the above-described liquid detecting device. The liquid container may be an ink cartridge mounted in the ink-jet recording apparatus.
Still another embodiment of the present invention is a module for use in detecting the liquid. This module includes a piezoelectric device and amounting structure. The piezoelectric device is used for detecting the consumption state of the liquid contained in the liquid container. The mounting structure is integrated with the piezoelectric device, an the piezoelectric device is mounted to the liquid container. In the mounting structure, there is particularly provided an opening cavity.
Still another embodiment of the present invention is a liquid container which houses the liquid. Though a typical liquid container is an ink cartridge, the present invention is not limited thereto. The liquid container is equipped with a piezoelectric device used for detecting the consumption state of the liquid contained in the container.
The opening cavity may penetrate a container wall. An intermediate member may be provided between the piezoelectric device and the container wall. The intermediate member seals off the opening cavity, and vibrates together with the piezoelectric device. A concave part formed in the internal surface of the container wall may serve as the opening cavity.
A communicating groove which communicates with the opening cavity may be provide so as to face the inside of the container. The communicating groove may be provided along a direction toward a supply port by which the liquid container supplies the liquid to the outside thereof.
The piezoelectric device may be inserted into a through hole provided in the liquid container in a tightly engaged manner. The through hole may be a hole formed by that the piezoelectric device breaks through a thin portion strained in a set-up position of the container wall.
The opening cavity may be provided in the close vicinity of a liquid absorbing member provided inside the container. The liquid absorbing member may comprise porous material member.
On the other hand, a liquid absorbing member which holds the liquid may be provided inside the opening cavity. The liquid absorbing member may comprise porous material member.
The piezoelectric device may include a piezoelectric element and a base member on which the piezoelectric element is formed, and the opening cavity may be formed on the base member.
The piezoelectric device may be mounted in the form of a mounting module integrated with the mounting structure. The mounting structure is of a structure that mounts the piezoelectric device to the liquid container. The opening cavity may be provided in a front face of the inside of the container in the mounting module.
An ink tank mounted in the ink-jet recording apparatus serves as a suitable liquid container. The ink tank may be provided on a carriage to which the recording head is mounted. The ink tank may be provided in a fixed section of the ink-jet recording apparatus. The ink tank is provided in the close vicinity of the recording head, and may communicate with the replaceable ink cartridge. The ink tank includes partition members which divide the inside of the tank into a plurality of chambers, and a plurality of the piezoelectric devices may be respectively provided in a plurality of the chambers.
This summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the above described features. The above and other features and advantages of the present invention will become more apparent from the following description of embodiments taken in conjunction with the accompanying drawings.